DEAR DR. DONOHUE: I don’t like exercising, and I have never done much of it. I am a 56-year-old woman, the mother of five boys who range in age from 16 to 33. All of them are athletic, as is my husband; I am not. It’s tough living in a house with only males. I have decided that I need to exercise. What is the absolute minimum I need in order to stay healthy? – R.O.

ANSWER: That’s a bit of a negative attitude, but I appreciate your honesty.

Most authorities say that for heart health, people must spend 30 minutes exercising at a heart rate that is 50 percent to 75 percent of their maximum heart rate and that such exercise should be done on most days of the week. The maximum heart rate is 220 minus a person’s age. For you, that’s a heart rate of 164 beats a minute. Half of that is only 82 beats a minute – about the heart rate of most people when resting. That’s not going to give you much exercise. If you go to 75 percent of the maximum heart rate, your exercising heart should beat 123 times a minute – more realistic.

Don’t start at this level, or at that amount of time. You can start very gradually with walking. You could take a year or longer to reach the goal of a heart rate of 123 for 30 minutes. You’re allowed to break exercise sessions into three 10-minute periods or two 15-minute ones.

Some insist on a full hour of exercise. That’s a bit much. Not many people can spare so much time.

No one, including you, should begin an exercise program in mid-life without first consulting a doctor. Exercising a heart that’s not fit to withstand it can cause big trouble.

If you want to limit exercise, walk. Work up to a pace of 3.5 miles an hour. You can still benefit your heart by walking at a slower pace. Any activity is better than no activity. Picking up the exercise tempo increases its benefits, but common sense has to prevail.

DEAR DR. DONOHUE: Will you explain a groin pull to me? The team trainer says I have one. I play shortstop, and I think I got it while sliding into third base. How long does it take to heal a pull? Can I do anything to speed things up? – B.M.

ANSWER: A “pull” is a muscle strain, and that means muscle fibers have been stretched beyond their ability to return to their normal length. Some fibers have been torn. It’s like pulling a rubber band beyond its elastic limits. The groin is the crease between the upper leg and the abdomen. The term “groin pull” is applied to torn muscle fibers of the inner, upper thigh muscles. Those are the muscles that let you make quick side movements.

Muscle pulls usually heal in two weeks. You’ll know things are OK when you are free of all pain. Don’t run until you’ve reached that point.

You can speed things up a bit by applying warm compresses for 15 minutes to the injured muscle. Do so three or four times a day.

DEAR DR. DONOHUE: I donate blood on a regular basis. I am scheduled to run a 10K race in one month. How close to the day of the race can I donate blood without ruining my chances of running well? – W.S.

ANSWER: The standard amount of blood taken is about 1 pint – 500 ml. You lose not only red blood cells when you give blood, but you lose fluid too. The fluid loss is quickly restored. It takes only three days, at most, to recover lost fluid.

Red blood cells are oxygen-carriers. Runners need oxygen. You would think that donating blood would truly upset a runner’s ability to sustain long distances. It takes much longer to restore the red-blood-cell population. However, after donating blood, highly trained distance runners experience only a small reduction in their running times. Lesser athletes suffer few consequences in their endurance. By one week, everyone is back to normal.

For those not familiar with the metric system, a 10K race is 6 miles.

DEAR DR. DONOHUE: My son, age 48, has worked for 25 years as a machinist. Lately his hands have broken out with a bad case of eczema. He has never had this affliction before. What caused it? The doctor said he should get a new job, which is impossible at his age. – A.F.

ANSWER: Eczema turns skin red and creates tiny blisters on the red skin. Often, the skin itches. There are varieties of eczema, and the kind your son has is probably the kind called irritant contact dermatitis. (Dermatitis is skin inflammation.) He must be using something in his job or at home that gets on his hands and causes the inflammatory reaction. Detergents, chemicals or other sorts of industrial materials are possibilities. Can he wear gloves and do his work? Plain latex gloves or rubber gloves with an inner lining might do the trick. “Barrier” creams, ointments, liquids or sprays can be applied to the hands to protect them from whatever the mischief-maker is. Kerodex cream, Hydropel ointment and Skin Shield (a liquid) are all nonprescription items that should be easy to find.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Readers may also order health newsletters from www.rbmamall.com